1. Field of the Invention
The present invention relates to the field of optimization of wireless network architectures and resource allocations.
2. Description of the Related Art
Optimization of network architectures is critical to achieve maximal network capacity and provide high quality services to the largest possible number of users. In common scenarios, multiple users share the wireless medium and engage in rather diverse applications such as video, voice, and FTP delivery. Optimizing allocation of resources across all users and applications maximizes the satisfaction of the users.
So far cross-layer optimization has been applied only to single application systems. However, in practice multiple users sharing the wireless medium, e.g. in a cell, often run different applications simultaneously. User satisfaction translates into a different set of requirements for each type of application. Furthermore, the impact of losses on the user-perceived quality is highly application-dependent.
The challenge of optimization across multiple applications has been treated mainly in the form of throughput maximization as described by V. Tsibonis, L. Georgiadis, L. Tassiulas, in “Exploiting wireless channel state information for throughput maximization,” IEEE INFOCOM 2003, in the following referred to as [Tsi01], and by Xin Liu, E. Chong, N. Shroff, in “Transmission scheduling for efficient wireless utilization,” IEEE INFOCOM 2001, in the following referred to as [Liu01].
Maximizing throughput leads to optimum performance only for applications, which are insensitive to delay, and packet loss. Multimedia applications such as video and voice are highly sensitive to changes in data rate, delay, and packet losses. Even the importance of a packet changes dynamically depending on the history of previous packets. Due to these reasons, throughput maximization leads to performance, which is usually not optimal with respect to user perceived quality for multimedia applications.
WO 00/33511 A describes a system for improving the end-user quality of service in a packet switched network. Reports are sent from various nodes in the network informing a network supervisor of the end-user quality of service at the node, which represents an estimate of the quality from a human end-user's perspective. The quality supervisor analyzes the reports and sends commands to the node, which sent the report and/or to other nodes in order to improve the end-user quality of service at the node and in the packet switch network as a whole. The nodes comprise sending and receiving terminals, routers and gateways. The reports include measurements of link parameters, device parameters and end-user quality of service.